Need advice on P0A94-555 DC/DC Converter Performance

Hi guys,
Would appreciate some advice on diagnosing problems with our Prius.

It's a 2006 package #7; bought it new. It has just under 220k miles now.

Notable mechanical repairs:
2014 114k miles: Recall replacements for Inverter water pump, steering extension shaft
2015 127k miles: Traction battery replaced under warranty. Also replaced engine water pump, drive belt.
2015 132k miles: Replaced PCV valve.
2021 191k miles: Replace brake actuator and resistor.

Recently, while our daughter was returning from a road trip (very hot conditions), the dashboard lit up and car exhibited reduced performance. Fortunately she was close to our parents house, and she was able to nurse it there, where it finally died.

I drove up there to collect diagnostic data and research the problem. It's an hour away, so I'm trying to prepare as much as possible in advance to take another trip to diagnose further. I'd appreciate advice and guidance from you all on solving this. Thanks!

Dashboard warning lights from the day of incident:


Dr Prius readout when parked at parents house:


Techstream read out from day of incident.


I didn't realize I should check freeze frame data, so I had to go back a few weeks later to do that. When I ran TechStream again, it showed the same codes, except for the Transmission C2318 code (low voltage error power supply malfunction):



Here's the freeze frame data showing the P0A94 555 detail code:



Here's the freeze frame data for the C1310 HV System Malfunction code:







Here's the diagnostic from the service manual for P0A94 555, which says to follow steps on HV-378:



And this is page HV-378:







For the P0A94 555 diagnostic on Page HV378, it appears that I'm supposed to check voltages at the I-10 connector in the inverter (a) when it's plugged in, and then (b) when it's disconnected. It would seem the diagnostic flow chart suggests replacing either the "Inverter with Converter Assembly" or "Hybrid Vehicle Control ECU."

Questions:
1) Does this sound correct?
2) How do you measure the voltages when the connector is plugged in? Can you access the pin from the back side of the connector? When it's unplugged, it's easy to stick a probe in the open hole.
3) How do activate the "ACTIVE TEST" in TechStream? I'm using an older version of TechStream on a PC.

Secondly, I'm assuming P0A94 is the primary concern. Is that correct? Do you think I need to worry about the HV codes? Would you suggest further diagnostics on these codes? Or are these just by-products of the P0A94 issues?

C1241 Low battery positive voltage or abnormally high battery positive voltage
C1259 HV system regenerative malfunction
C1310 HV system malfunction

I'm planning another trip up with my tools to remove the wipers/etc and crack open the inverter. I did this before, as I replaced the brake actuator myself.

I looked up the inverter, which appears very expensive to purchase new from Toyota. The Hybrid ECU I can't even find as a new part. Any thoughts on what to do with the parts would be appreciated. For my brake actuator I tried buying a "refurbished" part, which turned out to be garbage. I ended up just buying a new one from Toyota.

Any other thoughts, suggestions, etc would be greatly appreciated.

Thanks very much for your guidance!

 

Thanks guys, much appreciated.

Does anyone have input or experience on the diagnosis/etc that I posted above? Thanks much!